Exhaust gas recirculation is used to improve emission performance of diesel engines. Prior to being introduced into engine combustion chambers, the exhaust gas may be circulated through one or more EGR coolers. Due to the low temperature environment and flow characteristics of the EGR cooler, soot particles contained in the exhaust gas may be deposited onto walls of the EGR cooler to form a film of soot, often in a relatively short period of time, decreasing the heat transfer ability of the EGR cooler. As a result, the recirculated exhaust gas may not be effectively cooled and the ability of the recirculated exhaust gas to improve emission may be reduced.
Various methods have been utilized to address the issue of soot deposition in EGR coolers. In some examples, particulate filters and oxidative catalysts have been used to remove soot particles upstream of the EGR coolers. However, the particulate filters and oxidative catalysts may take up significant amount of space inside a cramped engine compartment, may require frequent maintenance and replacement.
In another example provided by U.S. Pat. No. 7,011,080 to Kennedy, a reverse airflow may be used to clean the EGR cooler. In this example, a single charge air cooler is utilized to cool the mixed charge air and recirculated exhaust gas. A flow valve that is movable between open, bypass, and reverse positions is used to control the flow of the mixed charge air and recirculated exhaust gas through the cooler. The reverse position of the flow valve provides a reverse cleaning flow through the cooling passages to remove soot particles accumulated in the cooler. However, the method provided by Kennedy may utilize contaminated exhaust air that contains soot particles for cleaning the EGR cooler, as well as increased complexity in the exhaust flow design through the EGR cooler.
To at least partially address the above issues, systems and methods for using compressed intake air that is free of soot particles to clean the EGR cooler of an internal combustion engine having a turbocharger are provided herein. One example system includes an EGR valve for selectively diverting a portion of exhaust gas through an EGR conduit to an intake side of the internal combustion engine, an EGR cooler disposed in the EGR conduit, the EGR cooler having an exhaust side and an intake side, and a compressed intake air delivery system including a compressed air conduit, the compressed intake air delivery system being configured to selectively divert a portion of compressed intake air compressed by the turbocharger through the EGR cooler to remove soot particles deposited in the EGR cooler. In some examples, a valve disposed in the compressed air conduit may control the flow of the compressed intake air. In other examples, the valve for controlling the compressed intake air flow through the compressed intake conduit may be eliminated, when the compressed air conduit may be sized and aimed in such a way that it does not interfere with flow of EGR gas into the EGR cooler, and that it is still possible to deliver the adequate amount of EGR flow for engine operation.
In this way, turbocharger pressurized intake air that is relatively free of soot particulate, and which is available from the engine turbocharger, may be used to purge through the EGR cooler to generate sufficient turbulence to dislodge soot particles deposited in the EGR cooler. In one example, the pressurized air may be used to remove cooler contaminants when EGR is not used for engine operation to reduce any disturbances to EGR flow operation.
This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure.